A conventional turbo-compressor applied to a turbo-refrigerating machine or the like includes an inlet guide vane that is a variable vane arranged at, for example, an inlet port to draw a fluid compressed by an impeller and adjust the flow rate of the fluid, a drive shaft that is connected to the inlet guide vane and is rotated to drive the inlet guide vane, a motor for driving the drive shaft, and a coupling for coupling the drive shaft with an output shaft of the motor. A related art is disclosed in, for example, Japanese Unexamined Patent Application Publication No. 2009-185716.
In such a turbo-compressor, the coupling consists of, for example, halved members that hold the drive shaft and the output shaft of the motor and are fixed together with a fall-off preventive bolt to completely fix the drive shaft and the output shaft of the motor together so that an axial center position of the drive shaft agrees with that of the output shaft of the motor and so that the torque of the motor is transmitted to the drive shaft.